1. Field of the Invention
The present invention relates to a disk drive, and more particularly, to an actuator latch system of a disk drive capable of locking an actuator at a predetermined position when a disk stops rotating and, thereby, preventing the actuator from being rotated by an external shock.
2. Description of the Related Art
A hard disk drive is a data storage device for a computer that uses at least one read/write head to reproduce data stored in at least one disk and/or to record data onto the disk. In such a hard disk drive, the read/write head performs a reading/writing while being moved to a desired position by an actuator, wherein the read/write head is floated at a predetermined height from a recording surface of a rotating disk.
When the hard disk drive is not in an operating state, that is, when the disk stops rotating, the read/write head is parked at a position outside of the recording surface of the disk, such that the read/write head does not strike or contact the recording surface of the disk. Such head parking systems are classified broadly into a contact start stop (CSS) type and a ramp loading type.
In the CSS type system, a landing zone in which data is not recorded is provided at an inner circumferential region of the disk, and the read/write head contacts the landing zone and parks at the landing zone. In the ramp loading type system, a ramp is installed at a position outside the disk, and read/write head is parked on the ramp.
However, in both the CSS type system and the ramp-loading type system, the actuator may arbitrarily rotate due to an external shock or vibration applied to the disk drive, thereby causing the head to be freed from the landing zone or the ramp, and contact the recording surface of the disk. When the head contacts the recording surface of the disk, the head and/or the recording surface of the disk may be damaged. Therefore, when the disk stops rotating, and the head is parked at the landing zone or on the ramp, it is necessary to lock the actuator at a predetermined position so that the actuator may not rotate arbitrarily. To this end, the disk drive is provided with various types of actuator latch systems.
A magnetic latch system is generally used in the CSS type system. The magnetic latch system locks the actuator at a desired position, that is, a parking position using a magnetic force of a permanent magnet. A strong magnetic force is required to provide a strong latch force for a stable latch locking of the actuator.
However, in order to operate the disk drive, the head moves to the recording surface of the disk, and, to this end, the locking of the actuator must be released. At this time, since the stronger the latch force is, the greater the torque applied to the actuator is, the actuator trembles while rotating due to the inertia thereof upon releasing the actuator from the locking state. In order to prevent this, although a brake is applied to the rotation of the actuator simultaneously upon releasing the actuator from the locking state, precise controlling of the actuator is very difficult. Therefore, with a conventional magnet latch system, the latch force of the magnet latch system is limited and, accordingly, the magnet latch system cannot properly withstand a strong external shock.
In order to solve the above discussed problem of the conventional magnet latch system, an inertial latch system using an inertial lever has been proposed. A conventional single lever type inertial latch system is shown in FIGS. 1 through 3.
Referring to FIG. 1, an actuator 10 that moves a read/write head for reproducing and/or recording data to a desired position on a disk is installed at a disk drive. The actuator 10 has a swing arm 12 joined to a pivot bearing to be able to rotate, and a suspension 13 installed at one end portion of the swing arm 12 to support a slider 14 mounted with the read/write head and to elastically bias the slider 14 toward the surface of the disk.
In addition, an inertial latch system 20 that locks the actuator 10 when the head is parked on a ramp 15 is provided at the disk drive. The inertial latch system 20 is comprised of a latch lever 21 pivoting due to the inertia thereof, a latch hook 22 provided at the leading end of the latch lever 21, a notch 23 provided at the swing arm 12 of the actuator 10, a crash stop 24 for limiting the clockwise rotation of the swing arm 12, and a latch stop 25 for limiting the clockwise rotation of the latch lever 21.
In the above conventional inertial latch system 20, when a clockwise rotational shock is applied to the disk drive, the swing arm 12 of the actuator 10 and the latch lever 21 pivot counterclockwise due to the inertia thereof, as shown in FIG. 2. Accordingly, the latch hook 22 is caught by the notch 23, and the swing arm 12 of the actuator 10 can pivot no more counterclockwise. To the contrary, when a counterclockwise rotational shock is applied to the disk drive, the swing arm 12 of the actuator 10 and the latch lever 21 pivot clockwise due to the inertia thereof as shown in FIG. 3. At this time, the swing arm 12 collides with the crash stop 24 while pivoting clockwise first, and rebounds from the crash stop 24 to pivot counterclockwise, and the latch lever 21 collides with the latch stop 25, and rebounds from the latch stop 25 to pivot counterclockwise too. Accordingly, the latch hook 22 engages with the notch 23 for the inertial latch system 20 to lock the actuator 10.
The conventional single lever type inertial latch system 20 having the above-described structure properly functions when a clockwise rotational shock is applied to the disk drive, and the swing arm 12 of the actuator 10 pivots counterclockwise. However, when a counterclockwise rotational shock is applied to the disk drive, the swing arm 12 and the latch lever 21 all rebound from the crash stop 24 and the latch stop 25, and the latch hook 22 and the notch 23 engage with each other. Therefore, when the rebounding of the swing arm 12 does not exactly coincide with the rebounding of the latch lever 21, the notch 23 provided at the swing arm 12 does not engage with the latch hook 22, and, therefore, the actuator 10 does not lock. Thus, with the conventional single lever type inertial latch system 20, it is difficult to securely lock the actuator 10 when a counter clockwise rotational shock is applied to the disk drive.
FIGS. 4 through 6 show a dual lever type inertial latch system intended to correct the above drawback of the conventional single latch lever system.
First, referring to FIG. 4, an inertial latch lever system for locking an actuator 30 is comprised of first and second latch levers 41 and 42 pivoting due to the inertia thereof, a latch pin 43 provided at the first latch lever 41, a latch hook 44 provided at the second latch lever 42, a notch 45 provided at a swing arm 32 of the actuator 30, and a crash stop 46 for limiting the clockwise rotation of the swing arm 32.
In the conventional dual lever type inertial latch system 40, when a clockwise rotational shock is applied to the disk drive, the swing arm 32 of the actuator 30 and the first and second latch levers 41 and 42 pivot counterclockwise due to the inertia thereof as shown in FIG. 5, accordingly the latch hook 44 is caught by the notch 45, and the swing arm 32 of the actuator 30 can pivot no more counterclockwise. To the contrary, when a counterclockwise rotational shock is applied to the disk drive, the swing arm 32 of the actuator 30 and the first latch lever 41 pivot clockwise due to the inertia thereof as shown in FIG. 6. At this time, the swing arm 32 collides with the crash stop 46 while pivoting clockwise first, and rebounds from the crash stop 46 to pivot counterclockwise. In addition, as the first latch lever 41 pivots clockwise, the latch pin 43 pushes the second latch lever 42 to pivot counterclockwise. Accordingly, the latch hook 44 of the second latch lever 42 hooks the notch 45, and, therefore, limits counterclockwise pivoting of the swing arm 32.
The conventional dual lever type inertial latch system 40 having the above-described structure functions stably for both clockwise and counterclockwise rotational shocks applied to the disk drive. However, since the inertial latch system 40 requires two latch lever 41 and 42, the structure thereof is complicated, the size thereof becomes greater, and, therefore, the inertial latch system 40 takes up greater space. Therefore, the manufacturing cost increases, the assembling operation requires more time, and it is difficult to apply the inertial latch system 40 to a compact mobile disk drive.
Further, since the above-mentioned conventional inertial latch systems 20 and 40 are designed for use with only a relatively strong rotational shock enough to cause the latch lever or the latch levers to pivot, it is difficult to reliably secure the inertial latch system against a weak shock or weak vibration.